In tinker time today Anika and I made a volcano. The first time it didn’t work because the bottle we were supposed to cover wasn’t covered enough. The second time, though, the sand and gravel was wet so it was easy to mould it around the bottle. That made it work. Now I think that if we mix a little water in the sand and gravel the volcano will work perfectly! You should try a volcano. It is easy to look up directions on the Internet.